Compact magnetic crawler vehicle with anti-rocking supports

ABSTRACT

A robotic vehicle for traversing surfaces is provided. The vehicle is comprised of a chassis supporting a magnetic drive wheel for driving and steering the vehicle and a stabilization mechanism. The magnetic wheel comprises two flux concentrator yokes and an axially magnetized hub extending therebetween. The hub includes a central housing configured to house a sensor probe and enhance the magnetic pull force of the wheel by providing a continuous pathway of high magnetic permeability material for magnetic flux to flow axially through the drive wheel. The stabilization mechanism comprises a front and rear facing support element moveably coupled to the chassis and configured to contact the surface and move symmetrically relative to the chassis thereby maintaining the vehicle and probe normal to the surface and providing stability to the vehicle while traversing surfaces regardless of surface curvature and vehicle orientation.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S. Pat. No.10,343,276 filed on Jul. 12, 2017, entitled COMPACT MAGNETIC CRAWLERVEHICLE WITH ANTI-ROCKING SUPPORTS, the contents of which is herebyincorporated by reference as if set forth in its entirety herein.

FIELD OF THE INVENTION

The present invention relates to robotic vehicles and, in particular,robotic inspection vehicles having a magnetic drive wheel.

BACKGROUND OF THE INVENTION

Routine inspection of equipment is critical in most industries in orderto ensure safety and optimize performance. For example, in the petroleumindustry and related fields, liquids and gases and mixtures thereof aretransported via pipelines and these materials are also stored in largetanks.

It is known in this industry that in order to maintain the integrity ofpipelines, storage tanks and the like, a sensor device can be employedto inspect such surfaces. In particular, an inspection vehicle can beused to travel across a surface of the target object (e.g., a pipe ortank) and record information about the quality of the pipe wall. Amajority of these inspection vehicles use ultrasonic or magnetic sensorsto carry out the inspection. Based on the recorded information, anycracks or other deficiencies in the surface being inspected (e.g., pipewall) can be detected and noted to allow for subsequent remedial actionto be taken.

In the past, there have been different inspection vehicle designs thatare used to inspect various structures, such as factory equipment,ships, underwater platforms, pipelines and storage tanks. If a suitableinspection vehicle is not available to inspect the structure, analternative is to build scaffolding that will allow people access toinspect these structures, but at great cost and danger to the physicalsafety of the inspectors. Past inspection vehicles have lacked thecontrol, maneuverability and compact packaging (i.e., size) necessary toinspect such surfaces effectively.

In addition, while there are a number of different sensors that can beused in such inspection vehicles, one preferred type of ultrasonicsensor is a dry coupled probe (DCP) that is configured to performultrasonic inspection of the surface to measure wall thickness anddetect corrosion. Dry coupled probes are typically built in the form ofa wheel in which a shaft (axle) is meant to be held fixed since theshaft has the transducer component rigidly embedded in it while an outertire rotates around the shaft. The shaft of the probe thus must be heldand positioned such that the transducer always points at the surface,meaning that the wheel is not titled in its roll and pitch directions.

Thus, one of the challenges in using a DCP is that the probe needs toalways be perpendicular (normal) to the surface being inspected and thiscan be a challenge while the inspection vehicle is mobile and navigatingthe surface. A further challenge is to maintain the probe in closeproximity or in contact with the surface being inspected. This isespecially difficult since the inspection vehicle can drivecircumferentially, longitudinally and helically on a pipe or tanksurface which means that the DCP has to be realigned to ensure that theDCP is normal to the surface being inspected regardless of the locationof the inspection vehicle.

The present invention provides a solution for providing vehicularmovement in non-gravity-dependent operations, where the impact ofgravity on vehicle movement can be minimized while still enablingversatile control. As well, the present invention is capable ofmaintaining stability and effectively navigating a variety of curvedsurfaces such as pipes and vessels, as this is one possible use of theinvention. The present invention is also directed to a mechanism(device/apparatus) that stabilizes, maintains an appropriate height ofthe sensor and normalizes the of the sensor (e.g., DCP) relative to thesurface being inspected when inspection is being performed and while theinspection vehicle is being steered and/or moved in a variety ofdifferent tracks along the surface despite a varying range of degrees ofcurvature of the surface.

It is with respect to these and other considerations that the disclosuremade herein is presented.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a magnetic roboticcrawler vehicle for traversing a surface is disclosed. The vehiclecomprises a chassis and a magnetic drive wheel that is mounted to thechassis such that the drive wheel extends in a lateral direction. Inaddition, the drive wheel comprises two spaced apart flux concentratingyokes that rotate about a rotational axis and an axially magnetized hubextending laterally between the two yokes. The yokes are configured tobe driven independently thereby driving and steering the vehicle alongthe surface. For reference, the vehicle has a longitudinal axis thatextends perpendicularly to the rotational axis in a front and backdirection and through the midpoint between the two yokes.

In addition, the vehicle further comprises a stabilization mechanismthat is coupled to the chassis. In particular, the stabilizationmechanism comprises a first “front facing” support element and a second“rear facing” support element configured to contact and move along thesurface during normal operation of the vehicle. The first and secondsupport elements are positioned on opposite sides of the drive wheelrelative to the rotational axis, and are positioned symmetrically withrespect to the longitudinal axis. The stabilization mechanism alsoincludes a support mechanism moveably coupling the first and secondsupport elements to the chassis. The support mechanism is configured tomove the first and second support elements relative to the chassis in atleast an up and down direction. In particular, the support mechanism ispassive in nature and moves the first and second support elements in theup and down direction in response to a curvature of the surface therebymaintaining the first and second support elements in contact with thesurface.

According to a further aspect, the vehicle further comprises one or moreposition sensors attached to one or more of the stabilization mechanism,the chassis and the drive wheel. The one or more position sensors areconfigured to measure a relative position between the stabilizationmechanism and either the drive wheel or the chassis. The vehicle furthercomprises a processor that, based on a known geometry of thestabilization mechanism and the drive wheel and the relative positionmeasured using the one or more sensors during execution of a prescribedmaneuver of the robotic crawler vehicle on the surface, is configured tocalculate a) an orientation of the robotic crawler vehicle relative tothe surface in view of a known geometry of the surface, and/or b)calculate a curvature of the surface.

According to a further aspect, the vehicle further comprises one or moreposition sensors attached to one or more of the sensor probe assembly,the chassis and the drive wheel. In particular, the one or more positionsensors are configured to measure a relative position between the sensorprobe assembly and the drive wheel. In addition, the vehicle furthercomprises a processor that, based on a known geometry of the sensorprobe assembly and the drive wheel and the relative position measuredusing the one or more sensors during execution of a prescribed maneuverof the robotic crawler vehicle on the surface, is configured tocalculate a) an orientation of the robotic crawler vehicle relative tothe surface in view of a known geometry of the surface, and/or b)calculate a curvature of the surface.

According to another aspect of the present invention, a magnetic roboticcrawler vehicle for traversing a surface is disclosed. The vehiclecomprises a chassis and a magnetic drive wheel that is mounted to thechassis such that the drive wheel extends in a lateral direction. Morespecifically, the drive wheel comprises two spaced apart fluxconcentrating yokes and an axially magnetized hub extending laterallytherebetween. The yokes rotate about a rotational axis and areconfigured to be driven independently thereby driving and steering thevehicle along the surface. For reference, a longitudinal axis of thevehicle extends perpendicularly to the rotational axis in a front andback direction and through the midpoint between the two yokes.

The axially magnetized hub extending laterally between the two yokescomprises one or more axially magnetized magnets, and a housing. Thehousing is composed of a ferromagnetic material and includes a leftwall, an opposing right wall and a one or more lateral walls extendingtherebetween along the rotational axis. In addition, the walls of thehousing are shaped to define an open chamber therein and the one or morelateral walls are shaped to define at least one opening therethrough.Furthermore, the chamber is provided at the midpoint between the twoyokes and the housing has a fixed position relative to the yokes suchthat the at least one opening faces downward toward the surface duringnormal operation of the vehicle.

The vehicle further comprises a stabilization mechanism that is coupledto the chassis, the stabilization mechanism comprising a first and asecond support element configured to contact and move along the surfaceduring normal operation of the vehicle. In particular, the first andsecond support elements being positioned on opposite sides of the drivewheel relative to the rotational axis and are positioned symmetricallyacross the rotational axis of the drive wheel and symmetrically withrespect to the longitudinal axis. Moreover, the stabilization mechanismincludes a support mechanism that moveably couples the first and secondsupport elements to the chassis. In particular, the support mechanism isconfigured to move the first and second support element relative to thechassis in at least an up and down direction. Moreover, the supportmechanism is passive in nature and moves the first and second supportelements in the up and down direction in response to a curvature of thesurface thereby maintaining the first and second support elements incontact with the surface.

According to another aspect of the present invention, a magnetic roboticcrawler vehicle for traversing a surface is disclosed. The vehiclecomprises a chassis and a magnetic drive wheel that is mounted to thechassis such that the drive wheel extends in a lateral direction. Morespecifically, the drive wheel comprises two spaced apart fluxconcentrating yokes and an axially magnetized hub extending laterallytherebetween. The yokes rotate about a rotational axis and areconfigured to be driven independently thereby driving and steering thevehicle along the surface. For reference, a longitudinal axis of thevehicle extends perpendicularly to the rotational axis in a front andback direction and through the midpoint between the two yokes.

The axially magnetized hub extending laterally between the two yokescomprises one or more axially magnetized magnets, and a housing. Thehousing is composed of a ferromagnetic material and includes a leftwall, an opposing right wall and a one or more lateral walls extendingtherebetween along the rotational axis. In addition, the walls of thehousing are shaped to define an open chamber therein and the one or morelateral walls are shaped to define at least one opening therethrough.Furthermore, the chamber is provided at the midpoint between the twoyokes and the housing has a fixed position relative to the yokes suchthat the at least one opening faces downward toward the surface duringnormal operation of the vehicle.

The vehicle further comprises a sensor probe assembly disposed at leastpartially within the chamber of the housing. In particular, the sensorprobe assembly comprises a dry coupled wheel probe and a sensor support.The wheel probe is configured to passively roll generally in a directionof travel of the vehicle along the surface. The sensor support moveablycouples the wheel probe to one or more of the housing and the chassis.In addition, the sensor support assembly is configured to passively movethe wheel probe relative to the housing in at least the up and downdirection in response to the curvature of the surface therebymaintaining the probe in contact with the surface during normaloperation of the vehicle.

The vehicle further comprises a stabilization mechanism that is coupledto the chassis, the stabilization mechanism comprising a first and asecond support element configured to contact and move along the surfaceduring normal operation of the vehicle. In particular, the first andsecond support elements being positioned on opposite sides of the drivewheel relative to the rotational axis and are positioned symmetricallyacross the rotational axis of the drive wheel and symmetrically withrespect to the longitudinal axis. Moreover, the stabilization mechanismincludes a support mechanism that moveably couples the first and secondsupport elements to the chassis. In particular, the support mechanism isconfigured to move the first and second support element relative to thechassis in at least an up and down direction. Moreover, the supportmechanism is passive in nature and moves the first and second supportelements in the up and down direction in response to a curvature of thesurface thereby maintaining the first and second support elements incontact with the surface.

These and other aspects, features, and advantages can be appreciatedfrom the accompanying description of certain embodiments of theinvention and the accompanying drawing figures and claims.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1A is a perspective-view diagram of a magnetic robotic crawlervehicle in accordance with one or more disclosed embodiments;

FIG. 1B is a perspective-view diagram of the magnetic robotic crawlervehicle of FIG. 1A in accordance with one or more disclosed embodiments;

FIG. 2A is a rear-view conceptual diagram of a magnetic drive wheel inaccordance with one or more disclosed embodiments;

FIG. 2B is a rear-view conceptual diagram of a magnetic drive wheel inaccordance with one or more disclosed embodiments;

FIG. 2C is a rear-view conceptual diagram of the magnetic drive wheel ofthe magnetic robotic crawler vehicle of FIG. 1A in accordance with oneor more disclosed embodiments;

FIG. 3A is a perspective-view diagram of a housing component of themagnetic drive wheel of FIG. 1A in accordance with one or more disclosedembodiments;

FIG. 3B is a perspective-view diagram of a magnetic drive wheel inaccordance with one or more disclosed embodiments;

FIG. 4 is a perspective-view diagram of a magnetic robotic crawlervehicle in accordance with one or more disclosed embodiments; and

FIG. 5 is a perspective-view diagram of a sensor probe assembly of amagnetic robotic crawler vehicle in accordance with one or moredisclosed embodiments; and

FIG. 6 is a side-view of a simplified schematic model of a roboticvehicle 100 traversing a pipe in accordance with one or more disclosedembodiments.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS OF THE INVENTION

By way of overview and introduction, a compact magnetic robotic crawlervehicle having anti-rocking supports is disclosed. The vehicle isconfigured to be capable of traversing ferromagnetic surfaces of almostany curvature with high dexterity and maneuverability regardless ofsurface geometry and orientation.

According to an aspect of the invention, the vehicle is comprised of amain chassis section including a magnetic drive wheel configured todrive the vehicle along a surface and steer the vehicle. Morespecifically, the magnetic wheel is an assembly that is generallycomprised of axially magnetized hub comprising magnetized disks or rings(hereinafter referred to as the “magnetized hub”) extending axiallybetween two ferromagnetic flux concentrator yokes having symmetricalsize and provided at the two ends of the magnetized hub. According to asalient aspect of one or more of the disclosed embodiments, themagnetized hub includes a central chamber section that is configured tohouse an inspection probe therein (i.e., within the chamber) and is madefrom a material having a high magnetic permeability. In other words, thechamber is designed with a dual purpose, namely, to host the sensor(s)and actuators while also minimizing low magnetic permeability regionsalong the magnetic flux lines that extending through the hub and theyokes. For instance, as further described herein, the chamber can beconstructed from a ferromagnetic material and designed to avoidsaturation of the chamber and leakage of flux.

In some configurations, the sensor can be a roller sensor probeconfigured to roll along a pipe surface and take sensor measurements.Furthermore, the probe is preferably supported by the chassis using avertically oriented spring loaded mechanism providing forself-adjustment of the probe position within the chamber in the up/downdirection relative to the surface. Accordingly, the chamber has at leastan open bottom (e.g., the side facing the pipe surface) such that theprobe can be held against, or close to, the surface during operation andmove upward and downward depending on the contour of the surface beingtraversed and inspected.

According to a further salient aspect, a stabilization mechanism is alsoattached to the chassis. The stabilization mechanism comprises front andrear facing support elements (e.g., extending perpendicularly to theaxis of the drive wheel) that serve to minimize rocking of the chassisabout the axis of the drive wheel. With respect to the stabilizationmechanism, the front and rear support elements are generally alignedalong the longitudinal axis of the crawler. Preferably, the supportelements are also moveable relative to the chassis. In someconfigurations the support elements can be mechanically coupled suchthat they move in unison relative to the chassis. The up and downmovement of the stabilization mechanism can be assisted by a spring thatpassively adjusts the height of the support elements depending on thecurvature of the surface. The spring assisted stabilization mechanismserves to maintain the front and rear support elements against thetraversed surface and, thus, maintains the chassis crawler in an idealupright position on the surface, as long as one or more of the supportpoints contact the pipe. In some configurations, the support elementscan be configured to move in unison relative to one another, forinstance, the two support elements can be coupled together with spurgears and the mechanism is spring loaded such that the two supportelements move relative to each other even amounts as the curvature ofthe traversed surface changes. In some implementations, magnets can beprovided at (or near) the front and rear support contact points to helpprevent the robot from detaching from the pipe. In addition, in someimplementations, one or more sensors can be provided at the front andrear contact points, for instance, to detect contact with the pipe anddetect undesired tilt of the robot.

The foregoing aspects of the crawler and, as further described herein,address multiple major challenges that are common in the development ofinspection crawlers while simultaneously reducing the overall size andweight of the inspection vehicle.

Referring to FIG. 1A, an exemplary robotic vehicle 100 in accordancewith an embodiment of the invention is shown from a rear and sideperspective view. As shown, the vehicle can be in the form of a magneticcrawler inspection vehicle (such as a robot as shown herein) that can becontrollably driven across the surface 111. For example, the vehicle 100can be a robotic device for inspection of one or more regions of thesurface 111 using one or more on-board sensor probes that can becontrolled by a user who can transmit control commands to the vehicle tocontrol the operation of the vehicle. In this manner, the user caneffectively drive the vehicle across the surface and can stop and steerthe vehicle as well. The vehicle can also be configured to driveautonomously as well.

The robotic vehicle 100 includes a first chassis section 112. A magneticdrive wheel 116 is connected to the first chassis section 112. Alsoconnected to the first chassis section 112 is a stabilization mechanism114, comprising a front support element 140 and a rear facing supportelement 138. As noted, the drive wheel is magnetized so as to allow therobotic inspection vehicle 100 to magnetically attach to a ferromagneticmetal surface 111, such as a metal pipe or metal storage tank and bemovable thereacross. Thus, the first chassis section 112 provides themeans for moving the vehicle 100 across the surface 111, while the frontand rear support points passively lead and follow the first chassissection while moving. It should be appreciated that, as furtherdescribed herein, the front and rear support elements can each comprisean assembly including one or more wheels, for instance, magnetic wheels,sensor probe wheels.

In the robotic vehicle's forward and rear-ward direction of travel,which is indicated by arrow “D,” the drive wheel 116 of the roboticvehicle rotates about its axis 154 in either direction indicated byarrow “R1” in response to a motor that propels the vehicle forward andbackwards. The axis of rotation 154 of the drive wheel is also referredto as the lateral axis 154, which runs widthwise through the firstchassis section. Perpendicular to the lateral axis and extendinglengthwise through the middle of the first chassis section (e.g.,parallel to a flat surface that the crawler is on and bisecting thevehicle into left and right sides/halves) is the longitudinal axis 150.Also shown in FIG. 1A is the perpendicular axis 152, which extendsperpendicularly to both the longitudinal axis and the lateral axis andis normal to the surface 111 (when the crawler is resting on a flatsurface).

It can also be appreciated that the drive wheel can be configured topropel the vehicle in the forward and rearward direction as well assteer the vehicle, as further described herein. It can be furtherappreciated that the drive wheel provides stability to the vehicle 100.In particular, the drive wheel can include a strong magnet which createsa pull force between the wheel and a ferromagnetic surface 111 on whichthe vehicle can be moved, and this structural arrangement assists inresisting tipping of the vehicle. In addition, the drive wheel can havea relatively wide stance, which further provides stability to thevehicle by resisting rolling or tipping about the longitudinal axis 150.

Although not shown, the first chassis section can include a controlmodule. The control module can include a motor, a drive assembly fortransferring mechanical power from the motor to the drive wheel 116, apower source (e.g., battery), and a controller 190 that, using aprocessor 192, can control the operation of the vehicle by processingsensed data, processing stored instructions, and/or processing controlinstruction/signals received from a remote computer/operator (notshown). The first chassis section 112 can also further include otheroperating parts including a steering mechanism.

Drive Wheel

FIG. 1B depicts the same vehicle 100 as FIG. 1A and highlightscomponents of the drive wheel 116 that is configured to propel and cansteer the vehicle 100. In some implementations, the drive wheel 116 cancomprise a magnetic wheel assembly including two spaced apart steelyokes, namely, a left yoke 117 and a right yoke 118, which areconfigured to act as magnetic flux concentrators. The magnetic drivewheel 116 can also include an axially magnetized cylindrical hub 120extending between the two yokes.

Additionally, although not always required, the yokes 117 and 118 arepreferably configured to be independently driven so as to be able torotate the two yokes differentially and thus achieve fullmaneuverability of the vehicle 100. For instance, in someimplementations, an angular contact bearing (not shown) sitting betweena non-rotating end of the magnetized hub 120 and a rotating yoke is oneexemplary way of achieving independent rotation. Other possibleconfigurations are envisioned, such as combining needle thrust bearingswith regular ball bearings (also not shown). Preferably, the bearingseat is configured to have the smallest possible airgap between arotating steel yoke and the adjacent side face of the magnetized hub andalso to maximize the overlap between the magnetized side face of the huband the portion of the steel yoke positioned across the air gap from it,this is in order to maximize the resulting pull force of the magneticwheel.

A configuration that allows one or more of the yokes of the drive wheel116 to rotate freely is useful when pivoting in place on the surface111. Such an arrangement allows rotation about truly a single point(e.g., the point of contact between the surface and the left or rightyokes, P0L and P0R, respectively) rather than the mid-point of the axleof the driving wheel (e.g., the intersection of axis 152 and the axis ofrotation 154). This arrangement can also prevent the driving wheel fromdamaging the surface as it slides through the rotation. Accordingly, thedrive wheel 116, and thus the robotic vehicle 100, can be controllablysteered in any number of directions along the surface 111 including, forexample and without limitation, circumferentially, longitudinally, in ahelical path and the like. Although the yokes are shown as having a flatrim profile 222, the yokes can also have a curved rim profile such thateach yoke contacts the surface at just one point regardless of thesurface's curvature. In some implementations, the rim can be knurledand/or textured or coated to provide grip. Such an arrangement canimprove the consistency of pull force and friction and can also improvethe performance of the drive mechanism and reduce the power consumptionof the drive wheel when pivoting.

FIG. 2A-2C are conceptual diagrams of exemplary drive wheel assemblies,in accordance with one or more embodiments of the invention. Forsimplicity, FIGS. 2A-2C are shown from a rear (or front) view and aresimplified in that they do not depict a first chassis section or astabilization mechanism. The main differences between the exemplarydrive wheel configurations depicted in FIGS. 2A-2C concern the designand construction of the axially magnetized hub extending between theyokes, as further described herein.

FIG. 2A depicts a basic configuration of an axially magnetizedcylindrical hub 220A, as would be understood by those in the field ofmagnetic wheels. In such a configuration, the cylindrical hub comprisesan axially magnetized magnet 225, which can comprise one or more disc,cylinder or ring magnets. The magnet is axially magnetized because themagnetization direction is along the axis of the magnet which, as shown,is aligned with the rotational axis/lateral axis 154. Accordingly, thenorth and south poles of the magnet, which are located at the end facesof the magnet, are adjacent to the inner surface 247 of the left yoke217A and inner surface 248 of the right yoke 218A, respectively. Asshown in FIG. 2A, the yokes and serve to concentrate the magnetic fieldsuch that it follows the path generally illustrated by the magnetic fluxloops 230A that loop continuously through the magnet 225, the yokes atboth ends thereof, and return through a medium (e.g., the surface 111 incontact with the yokes). Such a configuration provides a relatively highattractive force between the magnetic wheel assembly and the surface.

It should be noted that in applications using magnetic wheels it can bedesirable to have available physical space in the central region of thewheel for placement of actuators or sensors, however, introducing emptyspace requires the removal of magnetic material which naturally reducesthe pull force of the wheel by the removal of the magnetic material plusdisruption of the flux of the remaining magnetic material by forcingflux lines to flow through air or other materials having low magneticpermeability. FIG. 2B illustrates an exemplary configuration in whichthe cylindrical hub (e.g., hub 220B) includes a central section 240,which defines an open space near the midpoint between the left yoke 217Band right yoke 218B. Also shown are multiple axially magnetized magnets235 disposed between the left side of the central section and the leftyoke and between the right side of the central section and the rightyoke. As noted, the magnets can be one or more disc, cylinder or ringshaped magnets. FIG. 2B also illustrates the disrupted magnetic field(s)following along the paths generally illustrated by the magnetic fluxloops 230B, which each loop through half of the magnetized hub arespective yoke and the medium (e.g., the surface in contact with theyoke). As noted, such a configuration can provide a relatively weakerattractive force between the magnetic wheel assembly and the surface.

In accordance with one or more embodiments of the invention, FIG. 2C isa conceptual diagram illustrating the exemplary configuration of theaxially magnetized cylindrical hub 120 of vehicle 100 shown in FIG. 1A.As shown, the extending axially between the left yoke 117 and right yoke118 and that includes a central housing 250 defining an open chamber forhousing an inspection probe 130 therein. According to a salient aspect,the housing 250 is specifically configured to house the inspection probeat least partially within the open space defined by the exterior wallsof the housing, while also minimizing low magnetic permeability regionsalong the magnetic flux lines that preferably extend continuouslythrough the hub and the yokes.

More specifically, in one or more embodiments, the cylindrical hub 120includes a plurality of axially magnetized magnets, which can be in theform of one or more disc, cylinder or ring magnets. As shown in FIG. 2C,two magnets 260L, 260R are provided, although more or fewer magnets canbe used. Magnet 260L is disposed between a left side of the housing 250and the inner side surface 277 of the left yoke 117. Magnet 260R isdisposed between a right side of the chamber and the inner side surface278 of the right yoke 118. As noted, the yokes serve to concentrate themagnetic field. In addition, because the yokes 117 and 118 arepreferably independently rotatable while at least the housing portion250 is preferably not rotating (e.g., to keep the probe 130 consistentlypositioned relative to the surface 111), the yokes can be configured torotate independent of one or more portions of the hub. For instance, asnoted bearings configured to minimize the air gap (i.e., distance)between a rotating component of the wheel and an adjacent stationarycomponent can help to maximize the resulting pull force of the magneticwheel.

In some implementations, the housing 250 can be integrally formed withone or more of the magnets. In addition or alternatively, the housingcan be a separate structure. In cases where the housing is a separatestructure an end of the housing can be fixedly coupled to an adjacentmagnet such that the joined housing and magnet do not move relative toone another. In addition or alternatively, an adjacent magnet (or yoke)can be configured to rotate relative to the stationary housing.Alternative magnetic wheel configurations are possible, for instance,the housing can be adjacent to one or more of the yokes, rather thanbeing positioned between two magnets. In such a configuration, the oneor more magnets can be coupled to the yokes at another location, forinstance, the opposite side of the yokes.

As noted, the housing 250 can be specifically configured to minimize lowmagnetic permeability regions along the flux lines. In someimplementations, this is achieved by constructing the housing using aferromagnetic material. Moreover, the particular shape of the openchamber defined by the housing can be configured to avoid saturation ofthe chamber and leakage of flux. Accordingly, as shown in FIG. 2C, themagnetic field generated by the magnets and passed through the centralhousing 250 and concentrated by the yokes 117 and 118 into the surface111 can follow the path generally illustrated by the magnetic flux loops230C, which continuously through the length of the magnetized hub 120and each yoke and through the medium (e.g., the surface 111 in contactwith the yokes). It should be understood that the magnetic flux linesillustrated in FIGS. 2A-2C are simplified and shown merely for basicillustrative purposes. The particular way that the magnetic fieldbehaves in practice can depend strongly on many variables including thedimensions of the housing and the open chamber, the distance between themagnet rings and the target surface and the like.

FIG. 3A is a perspective view of an exemplary configuration of thecentral housing 250 in accordance with one or more embodiments. Thehousing 250 is an elongate structure extending generally in thedirection of the axis 154. The housing 250 is shaped to define an openchamber 255 and configured to house one or more actuators and/or sensorprobes (e.g., probe 130) therein. In the particular configuration shownin FIG. 3A, the housing 250 has an open bottom side, which preferablyfaces the inspected surface, and an opposing open top side such that thehollow interior chamber 255 extends entirely through a portion of thehousing in the up and down direction. The housing can thus be defined bya pair of opposing lateral walls, namely, the front wall 362 and backwall 364, which extend between a left end-wall 366 and right end-wall368, and thereby defining the open chamber 355. It should be appreciatedthat although the exemplary housing 350 is shaped like a hollow cylinderextending along the axis of rotation 154 with openings provided in a topside and opposing bottom side, the housing can have any number ofdifferent shapes. For instance as shown in FIG. 3B, which is aperspective view of an exemplary drive wheel 316 having spaced apartyokes, an axially magnetized hub that includes a central housing 350. Asshown, for example, the housing can have the form of an elongatestructure (e.g., a hollow cylinder) having an open bottom side (notshown). Alternative housing sizes and shapes can be used as well.

Returning to FIG. 3A, the housing 250 can be configured to house a probewithin an open chamber therein, while still enhancing the overallmagnetic pull force of the crawler on the pipe by creating a singlecontinuous pathway of high magnetic permeability material for magneticflux to flow through. Preferably, the housing is constructed using amaterial having high magnetic permeability, such as a ferrous material.The housing can also be configured to minimize low magnetic permeabilityregions between the ends of the housing and the adjacent component(s) ofthe magnetic drive wheel assembly (e.g., magnets or flux concentratingyokes that are adjacent to a respective end of the housing). As noted,minimizing the air-gap distance between the ends of the housing and theadjacent magnetic wheel components can improve the magnetic permeabilityof the housing. Increasing the area of the hub that faces the magneticfield source (be it the yokes or the magnet itself depending on thearrangement) can also help the hub carry more magnetic fluxtherethrough. Accordingly, providing end-walls having a sufficientsurface area facing the adjacent wheel components can also maximize theoverlap between the magnetized side face of the hub and the portion ofthe steel yoke positioned across the air gap from it thereby increasingthe magnetic saturation point of the hub 120.

Moreover, the size, shape and thickness of the one or more sidewalls(e.g., walls 364 and 362) extending between the end walls 368 and 366can be defined to improve the magnetic permeability of the housing 250,for instance, by having a sufficient thickness and shape thatfacilitates axially magnetizing the housing. In some embodiments, theoverall magnetic permeability of the housing can be further improved byminimizing the volume of the open chamber 255, which is an area ofrelatively lower magnetic permeability. For instance, the walls of thehousing can be constructed to provide a chamber that is as small aspossible while still housing the elements necessary to allow for thedesired motion of a probe 130 during operation. Avoiding the use ofnon-ferrous materials within the chamber, to the extent possible, canalso be beneficial.

Ultimately, the exemplary configuration of the cylindrical hub 120 andhousing 250 shown in FIGS. 2C and 3A provide a relatively highattractive force between the magnetic wheel 116 and the surface 111,while still providing a central chamber that is suitable for housing aprobe 130 at least partially therein.

It should be noted that the exemplary crawler vehicle 100 illustrated inFIG. 1A and further described herein preferably includes a cylindricalhub 120 and housing 250 as shown and described in relation to FIGS. 2Cand 3A, however, alternative hub configurations can be utilized, forinstance, the hub configurations shown and described in relation toFIGS. 2A and 2B and 3B.

Stabilization Mechanism

Turning now to FIG. 1A, the stabilization mechanism 114 can include afront support element 140 provided in-front of the first chassis section112 and a rear support element 138 provided behind the first chassissection (assuming that the vehicle 100 is traveling in the directionidentified by the arrow D). The support elements can be configured tolimit the amount that the first chassis section can pitch forward orbackwards about the axis 154 of the drive wheel 116, thereby maintainingthe chassis in an upright and, more preferably, normal position,relative to the surface.

In some configurations, the front and rear support elements arecentered, e.g., in line with the longitudinal axis 150 that extendsthrough the middle of the vehicle 100. However, alternatively, the frontand rear support elements can be offset from the vehicle's longitudinalcenterline.

The support elements can, for example and without limitation, comprise apassively rolling ball-caster. Alternative support elementconfigurations can be utilized, for instance, a wheel rotating about afixed rotational axis that is parallel to the rotational axis 154 of thedrive wheel. By way of further example, a support element can comprise apiece of rigid smooth plastic configured to slide along the surface 111.In such a case, preferably, a material having a low coefficient offriction can be used to facilitate the sliding of the front support andhelp prevent scratches on the surface. In addition, magnets can also beprovided along with the support elements, for instance, behind or aroundeach support element so as to assist in maintaining contact with thesurface. In addition, sensors can be provided at the front and rearcontact points so as to detect contact between respective supportelements and the pipe and detect undesired tilt of the robot. Thisinformation could be used by the crawler for various purposes, forexample, to trigger an alarm warning the operator of undesired tilt.

As noted, the support elements are preferably moveable relative to thefirst chassis section 112. For instance, in the exemplary configurationshown in FIG. 1A, the stabilization mechanism 114 can include a linkingstructure 162 having the shape of an upside down ‘U,’ wherein the firstand second support elements 138 and 140 are joined at respective ends ofthe vertically oriented shafts of the linking structure. In addition,the linking structure 162 can be moveably coupled to the chassis 112and/or the drive wheel 116 such that the support elements can moverelative to the chassis and/or wheel in one or more directions. Forinstance, FIG. 1A shows the linking structure 162 including front arerear shafts that are slidably mounted to the cylindrical hub 120 using arear linear bearing 164 and a front linear bearing (not shown) that areattached to the front and rear side of the housing 250. Accordingly, theshafts of the linking structure can slide linearly through the bearingsin the up and down directions (e.g., in the direction of axis 152) andthus moving the front and rear support elements up and down relative tothe surface 111.

Although the up and down movement of the support elements 138 and 140provided by the stabilization mechanism 114 is generally passive, themovement can be biased or assisted using tensioning springs and the likeso as to maintain the support elements in contact with the traversedsurface during operation. For example and without limitation, FIG. 1Adepicts two tensioning springs 170 that are each attached at one end tothe cylindrical hub 120 and attached at the other end to the linkingstructure 162. The spring tension applied between the drive wheel, whichis planted on the surface 111, and the sliding linking structure 162serves to maintain the first and second support elements 138 and 140 incontact with the surface 111, by effectively pulling the linkingstructure towards the surface during operation.

It can be preferable to configure the stabilization mechanism such thatthe downward force exerted by the stabilization mechanism does notovercome the magnetic force that maintains the drive wheel in contactwith the traversed surface. Alternatively, in a further aspect, strongpermanent magnets could be added in close proximity to the supportelements 138 and 140 such that they remain in contact with the traversedsurfaced either completely due to the magnetic force or by a combinationof magnetic force and force exerted from the crawler chassis. In eithercase, even if the magnets just offset a part of the force required forcontact, the crawler will be less likely to detach from the surface.

Moreover, although the downforce applied by the stabilization mechanismon the front and rear support elements assists in maintaining thesupport elements against the surface so as to keep the vehicle stable,it can be appreciated that in some instances this downward force can beovercome, thereby causing one or more of the support elements to breakcontact with the surface. For instance, in the case of traversing anobstacle on the surface, the front support element 140 can contact theobstacle, which offers some initial resistance until the downward forceof the stabilization mechanism 114 is counteracted thereby causing thefront support to temporarily detach from the surface and the vehicle torock back about the axis of the magnetic wheel and, thus, allowing thefront support to overcome the obstacle.

It should be noted that in the embodiment shown in FIG. 1A, theanti-rocking support elements move in parallel linear directions and arecoupled mechanically so as to move together. In addition oralternatively, the support mechanism can also be configured to providefor movement of the front and rear support elements at an angle relativeto one-another. In addition or alternatively, the front and rear supportelements can be configured to move independently. Moreover, the supportelements can be configured to have a degree of independent movement anda certain degree of linked movement.

In addition to using a stabilization mechanism that allows the front andrear support elements to move in unison relative to the chassis 112and/or drive wheel 116, the stabilization mechanism can also beconfigured to allow the front and rear support elements to also moverelative to one another. FIG. 4 depicts an exemplary configuration of avehicle 400 including a stabilization mechanism 414 that moveablysupports a front support element (not shown) and rear support element438. In particular, the stabilization mechanism includes a front facinglinking structure 462 and a rear facing linking structure 464 that eachhave an elongate C shape. The rear facing support element 438 and frontfacing support element (not shown) are mounted near the midpoint of thefront and rear facing linking structures, respectively. The ends of thefront and rear facing linking structures can be pivotally mounted to theleft side wall 482 and the right side wall 484 of the first chassisstructure 412. In addition, the front and rear linking structures can bemechanically coupled together, such that the linking structures areconfigured to pivot about respective pivot points in concert. Forexample, interlocking spur gears 466 and 468 can, respectively, becoupled to the ends of linking structures 462 and 464, which arepivotally joined to the chassis 412. Pivoting linking structures thatare coupled using complementary spur gears allows the front and rearsupport elements to move in an up and down direction relative to thefirst chassis section but along a slightly curved path as indicated byarrows P1 and P2, respectively. Thus, the movement is not limited toonly the up and down direction relative to the chassis but can include acurved path in which the support elements also move closer or furtherapart from one another.

As a result of the particular geometry of the linking structures andpivot points defining the stabilization mechanism 414, the front andrear support elements are moveable relative to first chassis section 112along arcs P1 and P2 in order to maintain the front and rear supportelements in contact with the surface 111, even as the curvature of thetraversed surface changes. For instance, the self-adjustingstabilization mechanisms allow the vehicle 400 to traverse pipes havinga wide range of diameters and in any direction.

Although the up and down movement of the support elements provided bythe stabilization mechanism 414 is generally passive, the movement canbe biased or assisted using one or more tensioning springs. For exampleand without limitation, FIG. 4 depicts a tensioning spring 470 extendingbetween the front and rear facing linking structures 462 and 464. Thespring tension applied between the two linking structures can assist inmaintaining the front and rear support elements 440 and 438 in contactwith the surface 111, by effectively pulling the linking structurestowards one another during operation.

As noted, mechanically coupling the anti-rocking stabilization elementssuch that they move symmetrically relative to the chassis and, optional,relative to one-another, can minimize undesired tilt/rocking of thecrawler due to force misbalance and maintains uprightness of the crawleron curved surfaces regardless of the radius of curvature (e.g., size ofthe pipe) or the orientation and position of the crawler on the surface,provided that the stabilization elements contact the pipe.

The exemplary stabilization mechanisms are provided as non-limitingexamples. Other stabilization mechanism configurations and other systemsand methods for providing downward force on front and rear stabilizingelements can be used without departing from the scope of the disclosedembodiments. In addition, actuators such as linear actuators and motorsacting instead of or in addition to the spring-like elements mentionedabove can be utilized to force the front and rear support elements downagainst the surface being traversed.

While the embodiment shown in FIG. 1A illustrates the anti-rockingsupport elements moving independently of the probe, alternatively, thestabilization mechanism 114 can be mechanically linked to the probeassembly and configured to maintain a prescribed relationship betweenthe motion of the probe, as further described below, and the motion ofthe support elements. Such a configuration can be beneficial inapplications where the geometry of the vehicle 100 and the contour ofthe surface 111 can require the support elements and the probe to moveat different rates to achieve normalized orientation of the probe and/orvehicle relative to the surface. In one exemplary configuration, a camcan be coupled to the stabilization mechanism and a cam follower can beattached to the probe. Moreover, the profile of the cam can be definedsuch that the follower drives the DCP up and down according to aprescribed non-linear relationship that maintains the probe in contactwith the pipe. In addition, the prescribed non-linear relationship canbe a function of the curvature of the surface (e.g., a pipe) and/or theorientation of the device on the surface.

Probe Assembly

As noted, in accordance with one or more embodiments of the invention,the magnetized hub 120 can include a housing 250 that is configured tohouse an inspection probe within a chamber 255 with minimal disruptionto the magnetic flux pathway (i.e. high magnetic permeability) acrossthe length of the housing and hub.

FIG. 5 is a close-up rear-perspective view of an exemplary probeassembly 130 of vehicle 100 shown in FIG. 1A. The probe assembly 130 isdisposed at least partially within the chamber 255 defined by thehousing 250 portion of the axially magnetized hub 120. As shown, theprobe assembly 130 can comprise a probe wheel 530 that rotates about acentral axle 535 oriented generally parallel to the drive wheel'srotational axis 154. Accordingly, the probe wheel 530 that is configuredto roll along the surface being inspected and take sensor measurements.The probe wheel can be any type of probe, for example, a dry-coupledultrasonic wheel probe. It should however be understood that, in otherapplications, different types of wheeled and non-wheeled sensors couldbe incorporated into the probe assembly.

Furthermore, the probe assembly is preferably moveable relative to thechassis 114. For instance, FIG. 5 illustrates a vertically orientedspring loaded support mechanism referred to as a probe carrier 540providing for self-adjustment of the probe's position within the chamber255 in the up/down direction relative to the surface 111. As noted, thechamber 255 has at least an open bottom (e.g., the side facing thesurface, not shown) such that the probe wheel 530 can be held in contactwith or close to the surface during operation and can move up and downdepending on the contour of the surface being traversed and inspected.

More specifically, the probe carrier 540 includes two vertical shafts560. Each shaft is joined near one end to a corresponding end of thewheel probe's axle 535. In addition, the shafts are each moveablycoupled to the chassis 112. For instance, FIG. 5 shows the shaftsslideably mounted to a top wall 512 of the chassis 112 using respectivelinear bearings 540. Accordingly, the linear bearings enable the shaftsto slide therethrough in the up and down directions.

Although the up and down movement of the probe assembly provided by theprobe carrier 540 is generally passive, the movement can be biased orassisted using springs and the like. For example and without limitation,FIG. 5 depicts springs 570 that are each disposed around a length of arespective shaft 560 and compressed between the chassis section 112 andthe probe assembly 130. The spring force pushing against the chassis andlinearly sliding shafts serve to maintain the probe wheel 530 in contactwith the surface by effectively pushing the probe assembly towards thesurface during operation and self-adjusting the height of the probewheel 530 to accommodate the curvature of the pipe and changes incurvature.

In addition or alternatively, the force maintaining the probe wheel 530against the surface can be provided using magnets, for instance, rollerwheel magnets disposed on the left and right side of the wheel 530 androtating about the same axis as the axle 535.

With regards to this aspect of the probe assembly 130, it should benoted that placing the wheel probe in the middle of the crawler (in botha left-right direction and front-to back direction) significantlysimplifies issues related to alignment of the probe against the pipe (acommon issue otherwise referred to as ‘normalization of the probe’).This placement of the probe basically reduces the normalization problemfrom a three Degree of Freedom challenge to a specific one DoF challengewhere the only challenge to overcome would be the rocking of the chassis(back and forth tilt) which is addressed by the anti-rockingstabilization mechanism described herein.

Furthermore, placement of the wheel probe in the center of the crawlercan eliminate issues related to the probe wheel 530 dragging sideways asit can occur in other crawlers (unless the probe is lifted off of thepipe before steering). Accordingly, the exemplary crawler vehiclesdisclosed herein are capable of continuously taking probe readings whilecarrying out any maneuver without needing to lift the probe off the pipe(i.e., by simply pivoting about the probe when steering).

The exemplary housing, probe assembly 130 and self-adjusting probecarrier 540 is provided as a non-limiting example, alternativeadjustable mounting systems can be used to support the wheel probe andprovide movement of the probe assembly in one or more degrees offreedom. As a further example, in some implementations, a steel housingcan include an open-bottom without an open top and having apseudo-prismatic vertical hollow region shaped to fit a spring-loadedprobe carrier mounted therein wherein the tolerances between the chamberand probe carrier allow for smooth movement of the probe within thehousing and through the opening while facilitating uninterrupted flow ofmagnetic flux axially through the housing.

With respect to the exemplary DCP probe implementation, normal contactis preferably maintained between the traversed surface 111 and therolling sensor probe wheel 530 because a dry coupled probe generallyrequires its internal transducer component to be normal to the inspectedsurface in order to acquire a clean measurement. Thus, as noted above,in accordance with the present invention, the up/down movement providedby the probe carrier 540 and the stabilization mechanism provide passivenormalization of the probe against the surface.

Moreover, the probe assembly is preferably configured to move linearlyin a vertical fashion so as to compensate for different surfacecurvatures and the fact that the curved surface creeps (e.g., curves orcrowns closer to the vehicle) in between the spaced apart wheel yokeswhen driving helically or longitudinally on a pipe.

Stabilization Function

The details of the exemplary vehicle 100, and more specifically thenormalization and stabilization characteristics of the vehicle 100, canbe further appreciated in view FIGS. 6-7, which are further discussedbelow with continued reference to FIGS. 1, 2C.

FIG. 6 is a side-view of a simplified schematic model of the exemplaryrobotic vehicle 100. FIG. 6 illustrates the geometric relationshipbetween the main contact points between the exemplary vehicle 100 and apipe surface. FIG. 6 further illustrates an approximation of theeffective cross-section 600 of the pipe, the cross section being alongthe robot's middle plane as the robot traverses helically on the surfaceof the pipe. For simplicity, the schematic diagram only illustrates thefollowing components:

-   -   P0 represents the contact point between the magnetic drive wheel        116 (only the circumference of the drive wheel is shown) and the        traversed surface 311.    -   P1 represents the rotational axis 154 of the magnetic drive        wheel 116.    -   P2 represents the contact point between the front-facing support        element 140 and the surface.    -   P3 represents the contact point between the rear-facing support        element 138 and the surface.    -   ⊖1 and ⊖2 correspondingly define the angles between the front        and rear support elements and the perpendicular axis 152 of the        vehicle.

As shown in FIG. 6, the effective cross section of the pipe correspondsto an ellipse. Furthermore, for a pipe of radius ‘r’, in the schematic,the elliptical cross section of a pipe is shown with a minor axis lengthof 2r and a major axis length of 2r/Sin(⊖Steer) where r represents thepipe diameter and ⊖Steer represents the orientation of the crawlerrelative to the centerline of the pipe.

It should be noted that ⊖Steer=π/2+nπ (for any integer n) corresponds tothe crawler driving circumferentially around the pipe in which case theellipse becomes a circle; furthermore, ⊖Steer=0 represents the crawlerdriving longitudinally (i.e., lengthwise) on the pipe in which case theellipse major axis become infinitely long. It should also be noted thatthe vehicle 100 includes main magnetic wheel assembly as the centralelement of the crawler and offers two symmetrically disposed contactpoints with the pipe (both represented by P0 in the side-viewschematic). As such, the contact point between the pipe and the drivewheel of the crawler should typically occur along the ellipse's minoraxis as shown in the diagram and not off of it (however, ⊖Steer=0 and⊖Steer=n/2 are special cases in which the foregoing statement isirrelevant).

As shown in FIG. 6, the contact point between the magnetic drive wheeland the ellipse is assumed to always occur along the ellipse's majoraxis. That is, as the vehicle follows a constant-pitch helical path onthe pipe, it does not move along the periphery of the ellipse; rather,identical elliptical cross sections constantly occur at every point asthe crawler moves. This is a naturally occurring phenomenon due to thefact that the drive wheel is magnetic and that it is designed to havetwo symmetrically separated contact points with the surface whicheffectively normalize the drive wheel relative to the surface.

With respect to the stabilization mechanism 114 of vehicle 100, asnoted, P2 and P3 represent contact points between corresponding frontand rear facing anti-rocking support elements 138 and 140 and the pipe.⊖1 and ⊖2 correspondingly define the angles between those supportelements and the perpendicular axis 152 of the robot. It can thus beappreciated that variables such as gravity and torque applied to drivethe vehicle can affect distribution of forces between P0, P2 and P3 andcan tend to rock the chassis either forward or backwards. In otherwords, such forces can work to make ⊖1≠⊖2. However, as long as P2 and P3are maintained in contact with the pipe and symmetrically disposed aboutthe crawler's mid-plane and the ellipse's minor axis, ⊖1 should remainequal to ⊖2 and will generally represent an upright crawlerconfiguration in which the axis 152 is maintained normal to the pipesurface.

The foregoing principles similarly apply to implementations, in whichthe anti-rocking support elements pivot or rotate about an axis that isparallel to the axis of the drive wheel, for instance the exemplaryvehicle 400 as shown and described in relation to FIG. 4. Ifanti-rocking supports that can move up/down independently are used, theuprightness of the crawler on the pipe (i.e. the absence tilt backwardsor forward about the axis 154) will be a function of the relative heightbetween the front and rear-support element.

As disclosed in connection with FIG. 1A and FIG. 4, in a preferredembodiment of the anti-rocking stabilization mechanism, the contactpoints P2 and P3 occur on the mid-plane of the crawler, in other words,on the plane of the 2-dimensional schematic diagram shown in FIG. 6,with P2 and P3 being symmetrically disposed relative to the ellipse'sminor axis. Nonetheless, the normalizing and stabilizing function can beachieved even if the front and rear support elements were designed suchthat P2 and P3 contacted the pipe off of the crawler's mid plane (i.e.,the plane extending through perpendicular axis 152 and longitudinal axis150), provided, however, that they were disposed in a symmetricalfashion relative to the mid plane (i.e. equally spaced from themid-plane on opposite sides of it). For instance, P2 and P3 could beprovided closer to respective yokes of the drive wheel, which areprovided near opposite sides of the vehicle, as long as theaforementioned symmetry constraint is met.

Calculating Surface Curvature and Vehicle Orientation

Moreover, in accordance with one or more embodiments of the invention,the vehicle 100 can include one or more sensors 194 configured tomeasure the height of the probe assembly 130 relative to the chassis inthe up/down direction represented by the perpendicular axis 154.Furthermore, the vehicle control computer (or an external computingdevice in communication with the robot) can be configured to use themeasured height of the probe and the known size and shape of the vehicle(e.g., the know distance of the drive wheel yokes and position relativeto the probe) to determine the pipe diameter as well as the orientationof the vehicle on the pipe. Exemplary systems and methods forcalculating surface curvature and the orientation of a device arefurther described herein and in co-pending and commonly assigned U.S.Pat. No. 9,360,311 for “System and Method for Calculating theOrientation of a Device” to Gonzalez et. al. filed on Nov. 25, 2014,which is hereby incorporated by reference as if set forth in itsentirety herein.

For instance, the control computer can determine the radius of the pipebeing inspected by: causing the vehicle 100 to perform a specificmaneuver, say, a 180 degree (or more) steering maneuver about thecontact point of one of the two yokes; measuring the relative probeheight using the sensors throughout the maneuver; capturing the highestrecorded location of the probe (which occurs at the longitudinalorientation with ⊖Steer=π/2+nπ); and calculating the radius of a circlethat coincides with the wheel yokes and the probe at the recorded heightbased on the known distance between the wheel yokes and the probe.Furthermore, if the pipe diameter is known, a similar approach can befollowed to determine the orientation of the crawler relative to thepipe centerline in real-time. In such an application, the probe heightreading would preferably be correlated to an ellipse instead of a circlein order to determine the orientation.

In a further aspect, the same technique for determining the diameter ofa pipe could be used to determine the diameter of a cylindrical vesselor storage tank. For instance, the crawler 100 can be deployed on thewall of the tank and it could perform the technique and multiplelocations on the wall thus determining multiple measurements of the tankdiameter for subsequent volume calibration purposes. In this case thesensor chamber could be fitted with a laser range finder instead of anultrasonic testing probe to accurately measure the distance to the tankwall.

Similarly, sensors 194 can also be installed on the vehicle 100 thatmeasure the configuration of the anti-rocking support elements (e.g.,position relative to the chassis and one-another) and this informationused to mathematically calculate the radius of a pipe or orientation.The relative position information of the support elements can be asupplemental or an alternative method of estimating the pipe size andvehicle orientation.

In a further aspect, parts of the crawler could be used as probingelements to take Cathodic Protection (CP) measurement readings. CathodicProtection measurements typically involve simple voltage measurementstaken between the surface of a pipe and a reference electrode mountedsomewhere on the pipe itself. Because the flux concentrating yokes aremade of metallic material, they can be configured to take thesemeasurements upon contact with the pipe. For example, the crawler wheelyokes can be fitted with sensors suitable for taking voltage readings onthe pipe surface, which can be referenced back to the pipe's referenceelectrode by an umbilical cord. In addition or alternatively, the frontand/or rear support elements can be fitted with sensors that aresuitable for taking cathodic protection measurements. In addition, inimplementations where the crawler is deployed underwater the referencingcan occur wirelessly. Moreover, for sub-sea applications the CP readingscan be taken as the voltage measured between the pipe surface and thesurrounding sea water and accordingly the crawler does not need to beelectrically connected to the reference electrode directly.

It should be understood that various combination, alternatives andmodifications of the present invention could be devised by those skilledin the art. The present invention is intended to embrace all suchalternatives, modifications and variances that fall within the scope ofthe appended claims.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising”, when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention. Therefore, the scope of the invention is indicated by theappended claims, rather than by the foregoing description. All changesthat come within the meaning and range of equivalency of the claims areto be embraced within their scope.

What is claimed is:
 1. A magnetic robotic crawler vehicle for traversinga surface, comprising: a chassis; a magnetic drive wheel mounted to thechassis, wherein the drive wheel extends in a lateral direction androtates about a rotational axis and, wherein a longitudinal axis of thevehicle extends perpendicularly to the lateral, rotational axis in afront and back direction; and a stabilization mechanism coupled to thechassis, the stabilization mechanism comprising: a first and a secondsupport element configured to contact and move along the surface duringnormal operation of the vehicle, the first and second support elementsbeing positioned on opposite sides of the drive wheel relative to therotational axis, and wherein the first and second support elements arepositioned symmetrically with respect to the longitudinal axis; and asupport mechanism moveably coupling the first and second supportelements to the chassis, wherein the support mechanism is configured tomove the first and second support elements relative to the chassis in atleast an up and down direction, wherein the up and down direction isgenerally perpendicular to both the longitudinal axis and the rotationalaxis.
 2. The magnetic robotic crawler vehicle of claim 1, furthercomprising: a housing extending along the rotational axis, wherein thehousing is shaped to define an open chamber therein and at least oneopening, and wherein the housing has a fixed position relative to thechassis such that the at least one opening faces downward toward thesurface during normal operation of the vehicle.
 3. The magnetic roboticcrawler vehicle of claim 1, wherein the support mechanism is passive innature and moves the first and second support elements in the up anddown direction in response to a curvature of the surface therebymaintaining the first and second support elements in contact with thesurface.
 4. The robotic vehicle of claim 2, further comprising: a sensorprobe assembly disposed at least partially within the chamber; and asensor support moveably coupling the sensor probe assembly to one ormore of the housing and the chassis, wherein the sensor support assemblyis configured to passively move the probe assembly relative to thehousing in at least the up and down direction in response to a curvatureof the surface thereby maintaining the probe assembly in contact withthe surface.
 5. The magnetic robotic crawler vehicle of claim 4, whereinthe sensor probe assembly comprises: a dry coupled wheel probeconfigured to passively roll generally in a direction of travel of thevehicle along the surface.
 6. The magnetic robotic crawler vehicle ofclaim 5, wherein the sensor support comprises one or more shaftssupporting an axle of the wheel probe and being coupled to one or moreof the housing and the chassis by at least one mount, wherein the atleast one mount is configured to allow the one or more shafts to moverelative to the housing in at least the up and down direction; and oneor more spring elements configured exert a force between at least thesensor probe assembly and one or more of the chassis and the housing,and wherein the force urges the wheel probe downward through the atleast one opening of the housing and into contact with the surface. 7.The magnetic robotic crawler vehicle of claim 1, wherein the first andsecond support elements are equidistant from the rotational axis of thedrive wheel, and wherein the first and second support elements are oneor more of: positioned in line with the longitudinal axis of thevehicle, and evenly spaced apart from the longitudinal axis on oppositesides thereof.
 8. The magnetic robotic crawler vehicle of claim 1,wherein the stabilization mechanism includes one or more linkagesmechanically coupling the first and second support elements, wherein theone or more linkages are configured to move the first and second supportelements symmetrically relative to the drive wheel in at least the upand down direction thereby maintaining the first and second supportelements in contact with the surface and the vehicle substantiallynormal to the surface.
 9. The magnetic robotic crawler vehicle of claim8, wherein the one or more linkages are configured to move the first andsecond support elements symmetrically relative to the drive wheel in thefront and back direction and in the up and down direction such that thefirst and second stabilization elements move along a respective curvedpath.
 10. The magnetic robotic crawler vehicle of claim 8, furthercomprising: one or more spring elements configured to exert a forcebetween at least one of the one or more linkages and one or more of thechassis, the drive wheel and another linkage, wherein the force urgesthe first and second support elements into contact with the surfacethereby urging the chassis into a normal position relative to thesurface.
 11. The magnetic robotic crawler vehicle of claim 4, whereinthe stabilization mechanism includes one or more linkages mechanicallycoupling the first and second support elements and is configured to movethe first and second support elements symmetrically relative to thedrive wheel in one or more directions, wherein the stabilizationmechanism is configured to maintain a prescribed relationship betweenthe motion of the first and second support elements and the motion ofthe probe assembly in the up and down direction.
 12. The magneticrobotic crawler vehicle of claim 1, wherein the support mechanismcomprises a first linkage supporting the first support element and asecond linkage supporting the second support element, wherein the firstand second linkages are moveably coupled to the chassis by one or moremounts, and wherein the first and second linkages are mechanicallycoupled so as to synchronize the motion of the first and the secondsupport elements in at least one direction relative to the chassisthereby maintaining the first and second support elements in contactwith the surface and the vehicle substantially normal to the surface.13. The magnetic robotic crawler vehicle of claim 12, wherein the one ormore mounts are selected from the group consisting of: a linear bearingconfigured to allow one of the first and second linkages to slidelinearly with respect to the chassis in one or more directions, and apivot configured to allow the one of the first and second linkages torotate about the pivot.
 14. The magnetic robotic crawler vehicle ofclaim 13, wherein the first and second linkages are rigidly joinedtogether such that the first and second support elements move inparallel.
 15. The magnetic robotic crawler vehicle of claim 13, whereinthe first and second linkages are mechanically coupled using one or morespur gears configured to synchronize the motion of the first and secondsupport elements in one or more directions relative to the chassis andin one or more directions relative to each other.
 16. The magneticrobotic crawler vehicle of claim 1, further comprising: one or moreposition sensors attached to one or more of the stabilization mechanism,the chassis and the drive wheel and configured to measure a relativeposition between the stabilization mechanism and either the drive wheelor the chassis; and a processor configured to calculate, based on aknown geometry of the stabilization mechanism and the drive wheel andthe relative position measured using said one or more sensors duringexecution of a prescribed maneuver of the robotic crawler vehicle on thesurface, one or more of: a) an orientation of the robotic crawlervehicle relative to the surface based on a known geometry of thesurface, and b) a curvature of the surface.
 17. The robotic crawlervehicle of claim 4, further comprising: one or more position sensorsattached to one or more of the sensor probe assembly, the chassis andthe drive wheel, wherein the one or more position sensors are configuredto measure a relative position between the sensor probe assembly and thedrive wheel; and a processor configured to calculate, based on a knowngeometry of the sensor probe assembly and the drive wheel and therelative position measured using said one or more sensors duringexecution of a prescribed maneuver of the robotic crawler vehicle on thesurface, one or more of: a) an orientation of the robotic crawlervehicle relative to the surface based on a known geometry of thesurface, and b) a curvature of the surface.
 18. A magnetic roboticcrawler vehicle for traversing a surface, comprising: a chassis; amagnetic drive wheel mounted to the chassis, wherein the drive wheelextends in a lateral direction and rotates about a rotational axis andis configured to drive and steer the vehicle along the surface, whereina longitudinal axis of the vehicle extends perpendicularly to therotational axis in a front and back direction and through a midpointbetween two yokes; and a stabilization mechanism coupled to the chassis,the stabilization mechanism comprising: a first and a second supportelement configured to contact and move along the surface during normaloperation of the vehicle, the first and second support elements beingpositioned on opposite sides of the drive wheel relative to therotational axis, wherein the first and second support elements arepositioned symmetrically across the rotational axis of the drive wheeland are positioned symmetrically with respect to the longitudinal axis;a support mechanism moveably coupling the first and second supportelements to the chassis, wherein the support mechanism is configured tomove the first and second support element relative to the chassis in atleast an up and down direction, wherein the support mechanism isconfigured to move the first and second support elements in a passivemanner in the up and down direction in response to a curvature of thesurface thereby maintaining the support elements in contact with thesurface.
 19. The magnetic robotic crawler vehicle of claim 18, whereinthe first and second support elements are positioned equidistant fromthe rotational axis of the drive wheel, and one or more of: in line withthe longitudinal axis of the vehicle, and evenly spaced apart from thelongitudinal axis on opposite sides thereof.
 20. The magnetic roboticcrawler vehicle of claim 18, wherein the stabilization mechanismcomprises: one or more linkages mechanically coupling the first andsecond support elements, wherein the one or more linkages are configuredto move the first and second support elements symmetrically relative tothe drive wheel in at least the up and down direction; and one or morespring elements configured exert a force between at least one of the oneor more linkages and one or more of the chassis, the drive wheel andanother linkage, and wherein the force urges the first and secondsupport elements into contact with the surface thereby urging thechassis into a normal position relative to the surface.